The present invention relates generally to systems and methods for manufacturing absorbent garment cores. More specifically, the present invention relates to a system and method for providing precise disposition of superabsorbent particles into an absorbent core.
Disposable absorbent garments such as infant diapers or training pants, adult incontinence products and other such products typically are constructed with a moisture-impervious outer backsheet, a moisture-pervious body-contacting inner topsheet, and a moisture-absorbent core sandwiched between the liner and backsheets.
Cost-effective materials for absorbent cores that display good liquid absorbency and retention are desirable. Superabsorbent particles (SAP) in the form of granules, beads, fibers, bits of film, globules, etc., have been favored for such purposes. Such SAP materials generally include polymeric gelling materials that are capable of absorbing and retaining even under moderate pressure large quantities of liquid, such as water and body wastes, relative to their weight. The SAP particles typically are distributed within a fibrous web of fluffed pulp material, which may comprise natural or synthetic fibers. Such absorbent structures commonly are referred to as fluff pulp/SAP cores.
Superabsorbent materials generally include water-insoluble but water-swellable polymeric substances capable of absorbing water in an amount that is at least ten times the weight of the substance in its dry form. In one type of superabsorbent material, the particles may be described chemically as having a back bone of natural or synthetic polymers with hydrophilic groups or polymers containing hydrophilic groups being chemically bonded to the back bone or an intimate admixture therewith. Included in this class of materials are such modified polymers as sodium neutralized cross-linked polyacrylates and polysaccharides including, for example, cellulose and starch and regenerated cellulose that are modified to be carboxylated, phosphonoalkylated, sulphoxylated or phosphorylated, causing the SAP to be highly hydrophilic. Such modified polymers also may be cross-linked to reduce their water-solubility.
However, in order for superabsorbent materials to function, the liquid being absorbed by the absorbent core must come in contact with unsaturated superabsorbent material. In other words, the superabsorbent material must be placed in a position to be contacted by liquid. Accordingly, various wicking materials often are used to xe2x80x9cwickxe2x80x9d moisture to one or more desired locations of the absorbent core of the garment. Likewise, it often is desirable to xe2x80x9ctargetxe2x80x9d the superabsorbent material in the absorbent core by controlling the distribution of superabsorbent material to provide local regions of the absorbent core that have greater superabsorbent material concentrations than others. Such concentrations may be along one or more of the absorbent core""s length, width and thickness. By targeting the superabsorbent material, superabsorbent material may be efficiently distributed in the absorbent core without reducing the ability of the absorbent core to absorb and store liquids. Since more superabsorbent material can be embedded in local regions of the absorbent core that are more likely to come into contact with body fluids or other liquids while less or no superabsorbent material is embedded in areas less likely to come in contact with body fluids or other liquids, less superabsorbent material generally is used overall, while the absorbent qualities of the absorbent core remain unaffected or may even improve.
In view of the benefits afforded by targeting superabsorbent material in absorbent cores, processes have been developed to target superabsorbent material during the manufacture of the absorbent core. However, due to inconsistencies and variances during these manufacturing processes, the timing of the targeting of the superabsorbent material into the absorbent core material relative to the timing of cutting devices used to cut the absorbent core material are haphazard at best. A small difference in frequency between the device used to target the superabsorbent material into the absorbent core material and the cutting device used to cut the absorbent core material into absorbent cores can amplify through successive iterations, resulting in a large error between an ideal targeting of the superabsorbent material and the actual targeting. This large error can result in the distribution of the superabsorbent material in an undesirable location of the resulting absorbent core.
Accordingly, an improved system and/or method for phasing the targeting of superabsorbent material would be advantageous.
It would be desirable to provide a system and method for depositing superabsorbent material into an absorbent core whereby the amount and position of the superabsorbent material can be controlled with relative accuracy. It also would be desirable for such a system and method to be able to deposit particulate matter in a manner that fewer rejected products are manufactured due to variations in the manufacturing process. Additionally, it would be desirable for such system and method to be efficient, easy to operate, and capable of operating at high line speeds.
In accordance with at least one embodiment of the present invention, a system for synchronizing a targeting of superabsorbent material into absorbent core material by a targeting device with a cutting of the absorbent core material by a cutting device is provided. The system includes a first sensor to obtain a measurement of a change in a concentration of the superabsorbent material over a segment of the absorbent core material, wherein the measurement is representative of a previous timing of the targeting device. The system also includes a second sensor coupled to the cutting device to determine the timing of the cutting device. Additionally, the system includes a drive control coupled to the first sensor and the second sensor, where the drive control adjusts the timing of the targeting device, and wherein the timing of the targeting device is adjusted by the drive control based on a comparison of the previous timing of the targeting device and the timing of the cutting device.